Magnetic random access memory with field compensating layer and multi-level cell

ABSTRACT

A spin toque transfer magnetic random access memory (STTMRAM) element comprises a reference layer, formed on a substrate, with a fixed perpendicular magnetic component. A junction layer is formed on top of the reference layer and a free layer is formed on top of the junction layer with a perpendicular magnetic orientation, at substantially its center of the free layer and switchable. A spacer layer is formed on top of the free layer and a fixed layer is formed on top of the spacer layer, the fixed layer has a fixed perpendicular magnetic component opposite to that of the reference layer. The magnetic orientation of the free layer switches relative to that of the fixed layer. The perpendicular magnetic components of the fixed layer and the reference layer substantially cancel each other and the free layer has an in-plane edge magnetization field.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to magnetic memory elementshaving magnetic tunnel junctions (MTJ) and particularly to improving theease of switching of the free layer of the MTJ to reduce the requisitevoltage and current for causing the free layer to switch magneticstates.

2. Description of the Prior Art

Magnetic random access memory (MRAM) is rapidly gaining popularity asits use in replacing conventional memory is showing promise. Magnetictunnel junctions (MTJs), which are essentially the part of the MRAM thatstore information, include various layers that determine the magneticbehavior of the device. An exemplary MTJ uses spin torque transfer toeffectuate a change in the direction of magnetization of one or morefree layers in the MTJ. That is, writing bits of information is achievedby using a spin polarized current flowing through the MTJ, instead ofusing a magnetic field, to change states or program/write/erase/readbits.

In spin torque transfer (STT) MTJ designs, when electrons flow acrossthe MTJ stack in a direction that is perpendicular to the film plane orfrom the pinned (sometimes referred to as “reference” or “fixed”) layerto the free (or storage) layer, spin torque from electrons transmittedfrom the pinned layer to the free layer orientate the free layermagnetization in a direction that is parallel to that of the referenceor pinned layer. When electrons flow from the free layer to the pinnedlayer, spin torque from electrons that are reflected from the pinnedlayer back into the free layer orientate the free layer magnetization tobe anti-parallel relative to the magnetization of the pinned layer.Thus, controlling the electron (current) flow direction, direction ofmagnetization of the free layer magnetization is switched. Resistanceacross the MTJ stack changes between low and high states when the freelayer magnetization is parallel or anti-parallel relative to that of thepinned layer.

However, a problem that is consistently experienced and that preventsadvancement of the use of MTJs is the threshold voltage or current usedto switch the free layer magnetization during a write. Such current andthreshold voltage requirements are currently too high to allow practicalapplications of the spin torque transfer based MTJ.

MTJs with perpendicular anisotropy, such that the magnetic moment of thefree layer and the fixed layer thereof are in a perpendicular directionrelative to the plane of the film, are more appealing than theirin-plane anisotropy counterparts largely due to the density improvementsrealized by the former. Existing perpendicular MTJ designs include afree layer whose magnetic orientation relative to a reference (“fixed”)layer, while perpendicular in direction, high coercivity field (Hc) ofthe free layer, at its edges, limits the reduction of the effective Hcof the free layer. Lower effective Hc of the free layer would alloweasier switching of the free layer and would lower the threshold voltageand current required to switch the magnetization of the free layer.

It is noted that the foregoing problem occurs due to the inconsistent Hcthroughout the free layer, as shown and discussed by way of a graphshortly. That is, perpendicular anisotropic field (Hk) of the free layerchanges relative to the position within the free layer such that thecenter of the free layer generally has a lower Hc than the outer edgesof the free layer with Hc essentially increasing from the center of thefree layer to its outer edges. Accordingly, efforts to lower theperpendicular anisotropic field (Hk) of the free layer in order to easeswitching result in lowering of effective Hc, undesirably increase theedge-to-center effective coercivity (Hc) ratio. The relationship betweenHk and Hc are as follows:

Hc=Hk−Hdemag  Eq. (1)

where Hdemag is the demagnetization field related to the magneticmoment, thickness, shape and size of the magnetic thin film

For a greater understanding of the foregoing problem, FIGS. 1-3 show arelevant portion of a prior art magnetic memory element and a graph ofits effective coercivity field performance.

FIG. 1 shows the relevant portion of a prior art magnetic random accessmemory (MRAM) element 10, which includes a reference layer 3, also knownas a fixed layer, a barrier layer 2, also known as a tunnel layer, and afree layer 1. This configuration is common and very well known in theart. The layers 1-3 are often times collectively referred to as amagneto-tunnel junction (MTJ). When an electron current is appliedthrough the layer 3 towards layer 1, for example during a writeoperation, the MRAM element 10 switches states where the magnetic momentof the layer 1 changes direction relative to the magnetic moment of thelayer 3, from a direction shown by the arrow 5 to a direction shown bythe arrow 6. Such a change in the layer 1 is also known as a change froman anti-parallel state, where the direction of the magnetic moment ofthe layer 1 is opposed to that of the layer 3 to a parallel state, wherethe direction of the magnetic moment of the layer 1 is in the samedirection to that of the layer 3. The resistance of the MRAM element 10changes according to its state and typically, such resistance is higherwhen the MRAM is in an anti-parallel state than when it is in a parallelstate.

Lowering the perpendicular Hk of the layer 1 would make switching of thestate of the MRAM 10 easier, however, as earlier noted, the effective Hcreduction, which would significantly ease switching of the state of theelement 10 is limited because of the high Hc present at the edges of thelayer 1. This is better noticed by the figures to follow.

FIG. 2 shows generally a top view 7 of the layer 1 of FIG. 2 and a sideview 8 of the layer 1 of FIG. 2. The layer 1 is shown to be 65 nanometers in diameter, by way of example, and 1.2 nano meters in thickness.In accordance with these measurements, the effective Hc, in kiloOrsteds, vs. the position along the diameter of the layer 1, in nanometers (nm), is shown in a graph in FIG. 3. Accordingly, FIG. 3 shows agraph of the effective Hc, represented by the y-axis, vs. the positionalong the diameter of the layer 1, represented by the x-axis, for thecase where the perpendicular Hk (p-Hk) is equal to 14.5 kilo Oersted(kOe), shown by the line 9 and for the case where the perpendicular Hkof the layer 1 is equal to 13 kOe, shown by the line 11. As shown, theeffective Hc increases going from the center of the layer 1 out to itsedge and this change gradually increase and at the far edge of the layer1. When decreasing the perpendicular Hk from 14.5 kOe to 13 kOe, theedge-to-center effective Hc ratio is undesirably increased from 1.6 to3.0.

Thus, the need arises for decreasing the perpendicular anisotropic fieldof the free layer of an MRAM yet avoiding a substantial increase in theeffective Hc of the MRAM in order to reduce the threshold voltage andcurrent required to operate the MRAM.

SUMMARY OF THE INVENTION

Briefly, a spin toque transfer magnetic random access memory (STTMRAM)element is disclosed for storing a state when electrical current isapplied to it. The STTMRAM element includes a reference layer, formed ona substrate, having a perpendicular magnetic component associatedtherewith that is fixed in one direction. A junction layer is formed ontop of the reference layer and a free layer is formed on top of thejunction layer and has a magnetic orientation, at substantially thecenter of it that is perpendicular relative to the substrate andparallel and switchable relative to the reference layer. Further, aspacer layer is formed on top of the free layer and a fixed layer isformed on top of the spacer layer, the fixed layer having aperpendicular magnetic component associated therewith that is fixed in adirection opposite to that of the reference layer. The free layer iscapable of switching its magnetic orientation relative to the fixedlayer when electrical current is applied to the STTMRAM element. Theperpendicular magnetic components of the fixed layer and the referencelayer substantially cancel each other and the free layer has amagnetization field at its edge that is in-plane relative to thesubstrate.

These and other objects and advantages of the present invention will nodoubt become apparent to those skilled in the art after having read thefollowing detailed description of the various embodiments illustrated inthe several figures of the drawing.

IN THE DRAWINGS

FIG. 1 shows the relevant portion of a prior art magnetic random accessmemory (MRAM) element 10, which includes a reference layer 3, also knownas a fixed layer, a barrier layer 2, also known as a tunnel layer, and afree layer 1.

FIG. 2 shows generally a top view 7 of the layer 1 of FIG. 2 and a sideview 8 of the layer 1 of FIG. 2.

FIG. 3 shows a graph of the effective Hc, represented by the y-axis, vs.the position along the diameter of the layer 1, represented by thex-axis, for the case where the perpendicular Hk (p-Hk) is equal to 14.5kilo Oersted (kOe), shown by the line 9 and for the case where theperpendicular Hk of the layer 1 is equal to 13 kOe, shown by the line11.

FIG. 4 shows the relevant portion of a spin torque transfer magneticrandom access memory (STTMRAM) element 30, in accordance with anembodiment of the present invention.

FIG. 5 shows a top view 35 of the layer 21 and a side view 37 of thelayer 21, in accordance with an embodiment of the present invention.

FIG. 6 shows the relevant magnetization fields of the layer 23, 22, 21,24 and 25 of the element 30, in accordance with an embodiment of thepresent invention.

FIG. 7 shows a graph 47 of the performance of the element 30, inaccordance with an embodiment of the present invention.

FIG. 8 shows a graph of the normalized switching voltage of the element30 as the in-plane magnetic edge field of its layer 21 increases.

FIG. 9 shows a graph of the performance of the element 30 when variouslevels of edge field, including none, are applied to the layer 21 of theelement 30.

FIG. 10 shows the relevant portion of a spin torque transfer magneticrandom access memory (STTMRAM) stack 55, in accordance with anembodiment of the present invention.

FIG. 11 shows the formation of the stack 55, in relevant part andaccordance with a method of the present invention, as two steps.

FIG. 12 shows the formation of the stack 30, in relevant part andaccordance with another method of the present invention, as two steps.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following description of the embodiments, reference is made tothe accompanying drawings that form a part hereof, and in which is shownby way of illustration of the specific embodiments in which theinvention may be practiced. It is to be understood that otherembodiments may be utilized because structural changes may be madewithout departing from the scope of the present invention. It should benoted that the figures discussed herein are not drawn to scale andthicknesses of lines are not indicative of actual sizes.

In an embodiment of the present invention, a spin toque transfermagnetic random access memory (STTMRAM) element and a method ofmanufacturing the same is disclosed. Relevant layers of the STTMRAMelement include a reference layer, formed on a substrate, with aperpendicular magnetic component that is fixed in one direction. Ajunction layer is formed on top of the reference layer and a free layeris formed on top of the junction layer and has a magnetic orientation,at substantially the center of it that is perpendicular relative to thesubstrate and parallel and switchable relative to the reference layer.Further, a spacer layer is formed on top of the free layer and a fixedlayer is formed on top of the spacer layer, the fixed layer having aperpendicular magnetic component associated therewith that is fixed in adirection opposite to that of the reference layer. The free layer iscapable of switching its magnetic orientation relative to the fixedlayer when electrical current is applied to the STTMRAM element. Theperpendicular magnetic components of the fixed layer and the referencelayer substantially cancel each other and the free layer has amagnetization field at its edge that is in-plane relative to thesubstrate.

In an alternative embodiment, a stack is formed of multiple STTMRAMelements where each element is formed on top of another element allowingthe stack to store more than one state. FIG. 4 shows the relevantportion of a spin torque transfer magnetic random access memory(STTMRAM) element 30, in accordance with an embodiment of the presentinvention. The STTMRAM element 30 is shown to include a reference layer23, sometimes referred to as a “fixed layer”, on top of which is formeda junction layer 22, sometimes referred to as a “barrier layer” or a“tunnel layer” or a “barrier tunnel layer” or a “tunnel barrier layer”,on top of which is formed a free layer 21, sometimes referred to as a“switching layer”, on top of which is formed a separator layer 24,sometimes referred to as a “spacer layer”, on top of which is formed afixed layer 25, sometimes referred to as a “reference layer”. It isunderstood that other layers, not shown in FIG. 4, may be and aretypically formed on top of the layer 25, below the layer 23 and/or inbetween any of the layers shown in FIG. 4.

The layer 23 is shown to have a magnetic moment (also known as magneticorientation) in a direction shown by the arrow 231, the layer 21 isshown to have a magnetic moment in a direction shown by the arrow 211and the layer 25 is shown to have a magnetic moment in a direction shownby the arrow 251. An electrical current is applied, either at 31 or at32, to the element 30 during read and write operations. The element 30is generally used to store digital information during write or programoperations and this information is read during read operations. Forthese operations, various devices are coupled thereto that are not shownin FIG. 4. For a description of these devices and methods of readingfrom and writing to the element 30, the reader is directed to U.S.patent application Ser. No. 11/674,124, filed on Feb. 12, 2007, by RajivYadav Ranjan, and entitled “Non-Uniform Switching Based Non-VolatileMagnetic Based Memory”, the disclosures of which are incorporated hereinby reference.

The element 30 has a perpendicular anisotropy in that the layer 21 has amagnetic moment that is perpendicular relative to that of the film ontop of which the element 30 is formed. Similarly, the layers 25 and 23have such a perpendicular anisotropy. The element 30 switches states andstores a digital value corresponding to the magnetic orientation of thelayer 21 in that when this orientation is parallel to the magneticorientation of the layer 23, the element 30 is in one state, generallyreferred to as “parallel”, and when the orientation of the layer 21 isnot parallel, or anti-parallel, relative to the orientation of the layer23, the element 30 is in another state. These different states resultfrom unique resistances across the MRAM stack. In this manner, thedigital value of ‘1’ or ‘0’ is distinguished during read/writeoperations.

The layers 23 and 25 are made generally of material that is known in theart to be used for such fixed layer. Similarly, the layer 21 is made ofmaterial typically used by the industry for making a free layer, as isthe layer 22 made of material known for making a tunnel layer. The layer24, in some embodiments, is a multi-layer, made of at least oneinsulating layer 33, shown in the exploded view of the layer 24 at theleft side of FIG. 4, and at least one conductive layer 34. While one ofeach of the insulating and conductive layers is shown, it is understoodthat ‘n’ number of such a configuration may comprise the layer 24, with‘n’ being an integer value. However, the conductive and insulatinglayers alternate is such that no two conductive layers are adjacent toeach other and no two insulating layers are adjacent to each other. Theinsulating layer being made of an insulating material, such as but notlimited to any of the following: alumina (Al₂O₃), magnesium oxide (MgO),silicon dioxide (SiO₂), and oxide of other metallic material and theconductive layer being a conductive material, such as any of thefollowing: ruthenium (Ru), tantalum (Ta), copper (Cu), silver (Ag), gold(Au) and any other metallic non-magnetic element or alloy. Thus, theconductive layer is non-magnetic. In alternative embodiments, theinsulating layer 33 is formed on top of the conductive layer 34.

In some embodiments, the layer 24 is a single layer made of anon-magnetic material. The make-up of the layer 24, coupled with theconfiguration of the element 30, particularly using the layer 25 on topof the layer 24, as shown, cause the presence of magnetic fields atsubstantially the outer perimeter (edges) of the layer 21 with each suchmagnetic field having an in-plane magnetic orientation. These in-planemagnetic fields at the outer edge of the layer 21 effectively reduce theeffect of the high perpendicular Hc, which, as previously discussed,prevents the free layer to readily switch magnetization states in priorart magnetic memories. Accordingly, switching between the states of theelement 30 is eased and in this respect requires lower threshold voltageand current. As is shown in FIG. 7 herein, approximately 70% reductionin voltage is realized by the embodiment of FIG. 4 over that of priorart structures.

FIG. 5 shows a top view 35 of the layer 21 and a side view 37 of thelayer 21, in accordance with an embodiment of the present invention.FIG. 5 shows a top view 35 of the layer 21 and a side view 37 of thelayer 21. As shown, in-plane magnetization field 36, appearing at theedges of the layer 21 are present despite the perpendicularmagnetization field 38, at substantially the center of the layer 21 thatis switchable for storing purposes. The field 36 helps reduce the effectof high perpendicular Hc at the edge of the layer 21 thereby causing thelayer 21 to switch with more ease.

FIG. 6 shows the relevant magnetization fields of the layer 23, 22, 21,24 and 25 of the element 30, in accordance with an embodiment of thepresent invention. The perpendicular magnetic fields, appearingsubstantially at the center, of the layers 23, 22, 24 and 25, are eachshown in a direction consistent with the arrows 45, 43, 44 and 46,respectively. Magnetization directions of layer 23 and layer 25 areperpendicular relative to the plane of the substrate and oppositerelative to each other and not necessarily required to follow thedepicted directions in FIG. 6 and in alternative embodiments are in areverse direction than that shown in FIG. 6.

The magnetization of the layer 25 creates the field shown by the arrow41 and the magnetization of the layer 23 creates the field shown by thearrow 42. The layer 23 is also shown to have significant in-planemagnetic components or fields 40, at its edges, in a direction shown bythe arrows associated with the fields 40. Similarly, the layer 25 isshown to have significant in-plane magnetic fields 39, at its edges, ina direction shown by the arrows of the fields 39. In the case of thelayer 21, the magnetic field of the layer 25 imposes onto the layer 21and is in large part perpendicular at substantially the center of thelayer 21 and the layer 23, as shown by the arrow 44, which extendsthrough the layer 24 such that the perpendicular magnetic field of thelayer 24 is substantially the same as that of the layer 25. Similarly,the magnetic field of the layer 23 onto the layer 21 is in large partperpendicular at substantially the center of the layer 21, as shown bythe arrow 43, which extends through the layer 22 such that theperpendicular magnetic field of the layer 22 is the same as that of thelayer 23.

The perpendicular magnetic fields of the layers 25 and 23 essentiallycancel each other while the in-plane magnetic field at the edges of thelayer 21, fields 39 and 40, enhance each other and therefore reduce theeffective Hc that would typically be present at the edges of prior artstructures. Accordingly, not only does the process of switching statesbecomes easier and requires less voltage and current, switching is alsoadvantageously substantially symmetrical.

Furthermore, by optimizing the spacing between the layers 25 and 21, themagnetic moment of the layers 23 and 25, the layer 21 can be made toswitch at different voltages due to a difference in the magnitude ofin-plane edge fields on the layer 21. For a greater understanding of theaffect of the edge field on the switching voltage, a graph is shown anddiscussed relative to FIG. 7 and FIG. 8. By increasing the thickness oflayer 24, layer 25 is further separated from the layer 21 therebycreating a weaker magnetic field in layer 21 than when the thickness oflayer 24 is not so increased. To still fully compensate for the verticalfield from layer 23 into the layer 21, magnetic moment of layer 25 canincrease. While the vertical field is compensated, the edge in-planefield from the layer 25 onto layer 21 is lower than before as thespacing of layer 21 and layer 25 increases. Thus, with a lower edgein-plane field on layer 21, layer 21 would switch harder than before.

FIG. 7 shows a graph 47 of the performance of the element 30 vs. aconvetional MRAM structure as in FIG. 1, in accordance with anembodiment of the present invention. Graph 47 is shown to have a y-axisindicative of the normalized resistance, in arbitrary unit (a.u.) in they-axis vs. an x-axis indicative of the normalized switching voltage, ina.u., of the voltage required to switch the free layer in a MRAMstructure from anti-parallel to reference layer, i.e. high resistance,state to parallel, i.e. low resistance, state, where the drop in thecurves marked the switching voltage of the free layer. The dashed lineshown at 48 is the performance of a conventional magnetic random accessmemory element as in FIG. 1 and the line, shown at 49, with circlesthereon is the performance of the element 30. As shown by the graph 47,the element 30 exhibits far lower switching voltage than its counterpartstructure. A reduction of more than 70% in the switching voltage isrealized.

FIG. 8 shows a graph of the normalized switching voltage of the element30 as the in-plane magnetic edge field of its layer 21 increases. Thegraph of FIG. 8 has a y-axis that represents the normalized switchingvoltage of the element 30 in a.u. and an x-axis that represents thein-plane edge magnetic field of the layer 21, in kOe. As shown, theswitching voltage reduces faster at higher in-plane edge magnetic fieldof the element 30. For example, at the normalized switching voltage of10, the edge field is approximately zero whereas at the normalizedswitching voltage of approximately 5.5, the edge field is approximately4. Thus, by controlling the edge field, the layer 21 can be made toswitch states at different voltages.

FIG. 9 shows a graph of the performance of the element 30 when variousstrengths of edge field, including none, are applied to the layer 21 ofthe element 30. The graph of FIG. 9 includes a y-axis representing thenormalized resistance, in a.u., of the element 30 relative to thenormalized voltage, in a.u., of the element 30, shown by the x-axis,when there is no in-plane edge field applied, shown at 50, and when anin-plane edge field of 1 kOe is applied, as shown at 51, and when anin-plane edge field of 2 kOe is applied, as shown at 52, and when anin-plane edge field of 3 kOe is applied, as shown at 53, and when anin-plane edge field of 5 kOe is applied, as shown at 54. As shown, withthe applied in-plane edge field increasing from none to 5 kOe, thevoltage required to switch the layer 21 advantageously decreases from10.4 to 3.2, which is approximately a 70% reduction.

FIG. 10 shows the relevant portion of a spin torque transfer magneticrandom access memory (STTMRAM) stack 55, in accordance with anembodiment of the present invention. The stack 55 is shown to includethe layers of the element 30 and on top of the layer 25 thereof is shownformed a spacer layer 34 on top of which is shown formed free layer 31on top of which is shown formed junction layer 32 on top of which isshown formed reference layer 33. The layers 21-23 form an MTJ 56 and thelayers 31-33 form an MTJ 57. Thus, MTJ 56 and 57 are stacked. Becausetwo MTJs form the stack 55, the stack 55 is capable of storing twostates. It is understood that the stack 55 may employ any number of MTJsand clearly, the more MTJs employed, the greater the number of statesthat can be stored in the stack 55. Thus, the stack 55 is considered tobe a multi-state element.

Similar to the layer 24, the layer 34 is non-magnetic, in one embodimentof the present invention, and is accordingly made of an insulating layeror a conductive layer. In other embodiments, the layer 34, again similarto the layer 24, is multi-layered and made of any number of alternatingoxide and conductive layers. The layers 31-33 are made of materialanalogous to that of the layers 21-23, respectively. In someembodiments, the thicknesses of the layers 31-33 are analogous to thoseof the layers 21-23, respectively, and in alternative embodiments, thethicknesses of the layers 31-33 are different than that of the layers21-23, respectively. The layers 23 and 33 have different magneticmoments in some embodiments, and similar magnetic moments in otherembodiments. Different moments cause different fields in the respectivefree layers and thus different edge fields and different switchingvoltages associated with each of the free layers, even when the freelayers are identical in material and/or thickness. The layers 24 and 34each have a different thickness relative to the other. The effectivein-plane edge magnetic field of the layer 21, as produced by the layers23 and 25, is different than the effective in-plane edge magnetic fieldof the layer 31, which is produced by the layers 25 and 33. This islargely due to the requirement of each of the layers 21 and 31 having aunique current density to switch, as known to those skilled in the art.That is, briefly, the MTJs of the stack 55 cause it to be a multi-stateelement where each MTJ's unique switching current density results in adifferent state being programmed to from a multi-level cell.Accordingly, the effective in-plane magnetic edge field of each of theMTJs must also be at a different strength.

Layer 25 in FIG. 10 is a single magnetic layer in some embodiments and amagnetic multilayer structure with magnetic layers interleaved bynon-magnetic layer in other embodiments. Such non-magnetic layer can bemetallic, or metal oxide, or interlacing of both.

FIG. 11 shows the formation of the stack 55, in relevant part andaccordance with a method of the present invention, as two steps. Afterthe formation of the layers of the stack 55, field 60 is applied to thestack 55 to magnetize the layers 23, 33 and 25 such that the directionof magnetization at the center of each of these layers is substantiallypointing in the same direction as the direction of magnetization at thecenter of the rest of these layers, as shown by the arrows 231, 331, and251, respectively. Also, the magnetic orientation at the center of eachof the layers 23 and 25 and 33 is parallel relative to that of theothers. Field 60 has an orientation consistent with the direction of thearrow shown at field 60. This completes Step 1 but in thisconfiguration, clearly, the magnetic fields at the center of the layers25 and 23 do not cancel each other. Thus, next, at Step 2, field 61 isapplied to the stack 55. The direction of the magnetic orientation offield 61 is consistent with the direction of the arrow shown at field61, which is opposite to that of field 60. Field 61 is lower in strengththan field 60 and only magnetizes the layer 25 to a direction that isopposite to that of the layers 23 and 33. In other embodiments, field61, while still lower than field 60, only magnetizes the layers 23 and33 such that these layers' magnetization orientation becomes opposite tothat of the layer 25, which is shown at Step 3. Thus, after Step 1,either Step 2 is performed or Step 3 is performed. It is noted that theforegoing method of forming the stack 55 can also be applied to theelement 30 when it is being manufactured.

In accordance with another method of forming the stack 55 and/or theelement 30, the field 60 is applied while the layers of thestack/element are being formed, during the MTJ deposition and annealing,readily known in the art. A temperature of greater than 200 degreesCelcuis during the annealing of the MTJ can be used during such aprocess.

FIG. 12 shows the formation of the stack 30, in relevant part andaccordance with another method of the present invention, as two steps.After the formation of the layers of the stack 30, as described relativeto FIG. 4, at step 1, field 70 is applied to the stack 30 to magnetizethe layers 23 and 25 such that the direction of magnetization of each ofthese layers is substantially pointing in the same direction as shown bythe arrows 231, and 251, respectively. At this point, the process eithercontinues to Step 2 or to Step 3. Assuming Step 3 is performed next,field 72 is applied to the stack 30. The direction of the magneticorientation of field 72 is consistent with the direction of theassociated arrows, which is opposite to that of field 70. Field 72 islower in strength than field 70 and in some embodiments only magnetizesthe layer 23 in the direction shown and in other embodiments magnetizesthe layer 25 in a direction substantially opposite to that of the layer23.

Alternatively, after Step 1, Step 3 is performed in a manner analogousto Step 2 except that the layer 23 has a magnetization direction that isopposite to that which it took on at Step 1 but remains opposite to thatof the layer 25 because the layer 25 is magnetized, in Step 3, in thesame direction as that which it took on at Step 1. At step 3, field 74is applied to the element 30 to effectuate the foregoing magnetizations.The direction of field 74, as shown, dictates the direction ofmagnetization of the layers 23 and 25, at Step 3.

In accordance with another method of forming the element 30, the field70 is applied while the layers of the stack/element are being formed,during the MTJ deposition and annealing, readily known in the art. Atemperature of greater than 200 degrees Celcuis during the annealing ofthe MTJ can be used during such a process. The fields 72 and 74 areapplied to the element 30 after the formation of the latter.

Although the present invention has been described in terms of specificembodiments, it is anticipated that alterations and modificationsthereof will no doubt become apparent to those skilled in the art. It istherefore intended that the following claims be interpreted as coveringall such alterations and modification as fall within the true spirit andscope of the invention.

1. A spin toque transfer magnetic random access memory (STTMRAM) elementconfigured to store a state when electrical current is applied theretocomprising: a reference layer formed on a substrate and having aperpendicular magnetic component associated therewith that is fixed inone direction; a junction layer formed on top of the reference layer; afree layer formed on top of the junction layer and having a magneticorientation, at substantially the center of the free layer that isperpendicular relative to the plane of the substrate, the free layerhaving edge magnetization field at its edges, the edge magnetizationfield having an in-plane magnetic orientation relative to the substrate,the free layer being capable of changing states by switching itsmagnetic orientation when electrical current is applied to the STTMRAMelement; a spacer layer formed on top of the free layer; a fixed layerformed on top of the spacer layer, the fixed layer having aperpendicular magnetic component associated therewith that is fixed in adirection opposite to that of the reference layer, the magneticorientation of the free layer being parallel and switching relative tothat of the fixed layer, wherein the perpendicular magnetic componentsof the fixed layer and the reference layer substantially cancel eachother.
 2. The STTMRAM element, as recited in claim 1, wherein the spacerlayer is made of a non-magnetic material.
 3. The STTMRAM element, asrecited in claim 1, wherein the spacer layer is multi-layered and madeof ‘n’ number of a combination of an insulating layer and a conductivelayer, wherein ‘n’ is an integer value.
 4. The STTMRAM element, asrecited in claim 3, wherein at least one of the insulating layers of thespacer layer is formed on top of the free layer and at least one of theconducting layers of the spacer layer is formed on top of the insulatinglayer.
 5. The STTMRAM element, as recited in claim 3, wherein at leastone of the conducting layers of the spacer layer is formed on top of thefree layer and at least one of the insulating layers of the spacer layeris formed on top of the insulating layer.
 6. The STTMRAM element, asrecited in claim 3, wherein at least one of the insulating layers of thespacer layer is made of a material selected from a gropu consisting of:alumina (Al₂O₃), magnesium oxide (MgO), and silicon dioxide (SiO₂). 7.The STTMRAM element, as recited in claim 3, wherein at least one of theconductive layers is made of a metallic non-magnetic element or alloy.8. The STTMRAM element, as recited in claim 3, wherein at least one ofthe conductive layers is made from a material selected from a groupconsisting of: ruthenium (Ru), tantalum (Ta), copper (Cu), silver (Ag),and gold (Au).
 9. The STTMRAM element, as recited in claim 1, whereinthe perpendicular magnetic component of the reference layer and theperpendicular magnetic component of the fixed layer are eachsubstantially in the center of each respective layer and each layer hasan in-plane edge magnetic field that is substantially at the edgethereof that collectively produce the in-plane edge magnetization fieldof the free layer.
 10. A spin toque transfer magnetic random accessmemory (STTMRAM) element configured to store a state when electricalcurrent is applied thereto comprising: a reference layer formed on asubstrate and having a perpendicular magnetic component associatedtherewith that is fixed in one direction; a junction layer formed on topof the reference layer, the junction layer having significant in-planemagnetic components at its outer edges, the junction layer furtherhaving a magnetic component that imposes onto the free layer and is inlarge part perpendicular at substantially the center of the junctionlayer, which extends through the junction layer such that theperpendicular magnetic field of the junction layer is substantially thesame as that of the junction layer; a free layer formed on top of thejunction layer and having a magnetic orientation that is switchable andat substantially the center of the free layer and is perpendicularrelative to the plane of the substrate, the free layer having edgemagnetization field at its edges, the edge magnetization field having anin-plane magnetic orientation relative to the substrate; a spacer layerformed on top of the free layer; and a fixed layer having aperpendicular magnetic component and formed on top of the spacer layer,the fixed layer having a perpendicular magnetic component associatedtherewith that is fixed in a direction opposite to the direction ofmagnetization of the reference layer, the magnetic orientation of thefree layer being parallel and switching relative to that of the fixedlayer, the fixed layer having significant in-plane magnetic fields atits outer edges, the fixed layer imposing a magnetic field onto the freelayer that is in large part perpendicular at substantially the center ofthe free layer and extending through the spacer layer such that theperpendicular magnetic field of the spacer layer is substantially thesame as the perpendicular magnetic component of the fixed layer, theperpendicular magnetic components of the fixed layer and junction layersubstantially canceling each other and the in-plane magnetic field atthe edges of the free layer and the fields at the outer edges of thefixed layer and the junction layer enhancing each other thereby easingswitching of the free layer.
 11. The STTMRAM element, as recited inclaim 10, wherein the spacer layer is made of a non-magnetic material.12. The STTMRAM element, as recited in claim 10, wherein the spacerlayer is multi-layered and made of ‘n’ number of a combination of aninsulating layer and a conductive layer, wherein ‘n’ is an integervalue.
 13. The STTMRAM element, as recited in claim 12, wherein at leastone of the insulating layers of the spacer layer is formed on top of thefree layer and at least one of the conducting layers of the spacer layeris formed on top of the insulating layer.
 14. The STTMRAM element, asrecited in claim 12, wherein at least one of the conducting layers ofthe spacer layer is formed on top of the free layer and at least one ofthe insulating layers of the spacer layer is formed on top of theinsulating layer.
 15. The STTMRAM element, as recited in claim 12,wherein at least one of the insulating layers of the spacer layer ismade of a material selected from a group consisting of: alumina (Al₂O₃),magnesium oxide (MgO), and silicon dioxide (SiO₂).
 16. The STTMRAMelement, as recited in claim 12, wherein at least one of the conductivelayers is made of a metallic non-magnetic element or alloy.
 17. TheSTTMRAM element, as recited in claim 12, wherein at least one of theconductive layers is made from a material selected from a groupconsisting of: ruthenium (Ru), tantalum (Ta), copper (Cu), silver (Ag),and gold (Au).
 18. A method of manufacturing a spin toque transfermagnetic random access memory (STTMRAM) element comprising: Forming afirst reference layer on top of a substrate; Forming a first junctionlayer on top of the first reference layer; Forming a first free layer ontop of the first junction layer, the first free layer having aswitchable perpendicular magnetic component; Forming a first spacerlayer on top of the first free layer; Forming a fixed layer on top ofthe first spacer; Forming a second spacer layer on top of the fixedlayer; Forming a second free layer on top of the second spacer layer,the second free layer having a switchable perpendicular magneticcomponent; Applying a first magnetic field to magnetize each of thefirst and second reference layers in the same direction as each otherand each being perpendicular; and Applying a second magnetic field thathas a lower strength than that of the first magnetic field and in adirection opposite to that of the first magnetic field to magnetize thefixed layer.
 19. A method of manufacturing a spin toque transfermagnetic random access memory (STTMRAM) element comprising: Forming afirst reference layer on top of a substrate; Forming a first junctionlayer on top of the first reference layer; Forming a first free layer ontop of the first junction layer, the first free layer having aswitchable perpendicular magnetic component; Forming a first spacerlayer on top of the first free layer; Forming a fixed layer formed ontop of the first spacer layer; Forming a second spacer layer on top ofthe fixed layer; Forming a second free layer on top of the second spacerlayer, the second free layer having a switchable perpendicular magneticcomponent; Applying a first magnetic field to magnetize each of thefirst and second reference layers in the same direction as each otherand each being perpendicular; and Applying a second magnetic field thathas a lower strength than that of the first magnetic field and in adirection opposite to that of the first magnetic field to magnetize thefirst and second reference layers.
 20. The method of manufacturing, asrecited in claim 19, wherein the fixed layer has a perpendicularmagnetic component.
 21. A spin toque transfer magnetic random accessmemory (STTMRAM) element, configured to switch when electrical currentis applied thereto for storing a state comprising: A first magnetotunnel junction (MTJ), formed on top of a first reference layer andhaving a first free layer having a perpendicular magnetic component thatis switchable to define the state of the first MTJ, the first free layerfurther having in-plane edge field, the first reference layer having aperpendicular magnetic component; A first spacer layer formed on top ofthe first MTJ; A fixed layer formed on top of the first spacer, thefixed layer having a perpendicular magnetic component that is fixed; Asecond spacer layer formed on top of the fixed layer; A second MTJformed on top of the second spacer layer, the second MTJ having a secondfree layer having a perpendicular magnetic component that is switchableto define the state of the second MTJ the second free layer furtherhaving in-plane edge field, the strength of the in-plane edge field ofthe first free layer and the strength of the in-plane edge field of thesecond free layer being different.
 22. A spin toque transfer magneticrandom access memory (STTMRAM) element, as recited in claim 21 whereinthe first free layer has associated therewith a current density and thesecond free layer has associated therewith a current density, whereinthe current density of the first free layer is different from thecurrent density of the second free layer.
 23. A method of manufacturinga spin toque transfer magnetic random access memory (STTMRAM) elementcomprising: Forming a reference layer on top of a substrate; Forming ajunction layer on top of the reference layer; Forming a free layer ontop of the junction layer, the free layer having a switchableperpendicular magnetic component; Forming a spacer layer on top of thefree layer; Forming a fixed layer on top of the spacer layer, Applying afirst magnetic field to magnetize each of the reference and fixed layersin the same direction as each other, the direction of magnetization ofeach of the fixed and reference layers being perpendicular; and Applyinga second magnetic field that has a lower strength than that of the firstmagnetic field and in a direction opposite to that of the first magneticfield to magnetize the fixed layer.
 24. A method of manufacturing a spintoque transfer magnetic random access memory (STTMRAM) elementcomprising: Forming a reference layer on top of a substrate; Forming ajunction layer on top of the reference layer; Forming a free layer ontop of the junction layer, the free layer having a switchableperpendicular magnetic component; Forming a spacer layer on top of thefree layer; Forming a fixed layer on top of the spacer layer, Applying afirst magnetic field to magnetize each of the reference and fixed layersin the same direction as each other, the direction of magnetization ofeach of the fixed and reference layers being perpendicular; and Applyinga second magnetic field that has a lower strength than that of the firstmagnetic field and in a direction opposite to that of the first magneticfield to magnetize the reference layer.